Part 2 - Illumination

One of the most important things when you are working with integration of the 3d and real photos is the scene illumination. We need to illuminate it in a same way so that the objects are receiving the same lights that we see in the photograph. At this photo we can see that the sun light is very soft and the shadows are kinda diffused.

Knowing that, we can start thinking about what kind of light we are going to use, at this situation a smooth one, then I decided to use a skylight because it reproduces the sky light only and not a direct light like we see from sun, another advantage of the skylight is that it has a slot where we could load our HDRI and with that create a illumination similar to that one created by the sky of the backplate. Our skylight configuration is like that for now:



There’s an interesting thing about HDRI, it comes with a configurable parameter called “White Point” that shows up when we import it to our material editor, if we let this “White Point” with high values only high luminosity points will be used on our skylight, that’s perfect for us now because we gonna get a soft illuminated scene, for the car paint shader these values must be different but it´s not the time to worry about.


If we render our scene now with default white materials we gonna get this result:



With this render we could know if the skylight illumination is ok for our needs, realize that the blue and pink colors from sky are here because of the HDRI map applied to the skylight, but our shadows are too diffuse even for a scene with low sunlight, to solve this problem we are going to use another very interesting shader called Ambient Occlusion or only “AO”.

Our ambient occlusion shader is going to make our shadows stronger where the light hits the objects indirectly solving our problem of the car “flying” over the ground, but at this work we have another problem, there’s no motive for us to apply the AO shader on the plane because its not our true ground, our true ground is at the photo on our Background but again thanks to another brilliant mind at Mental Images the Matte Shadow shader from Mental Ray comes with an integrated AO solution.

Now let’s start configuring this “Matte Shadow” shader:


After applying this material to our plane we get the car totally integrated with the ambient and we also get the AO solution that literally puts the car on the ground, let’s render it now and see what we get:



To finish our work inside 3ds max now we need to create the materials for our car.